The short answer is of the full game released by Blizzard Entertainment. However, there are specific legal ways to access the game if you have previously owned it or if you use specific subscription services.
If you still have your original Reign of Chaos and The Frozen Throne CD keys, you can link them to your Battle.net account to gain access to the "Classic" version within the modern launcher for free. Warcraft III Free Download
Navigate to the "Games" section and find Warcraft III: Reforged . The short answer is of the full game
Download and install the Battle.net App. Warcraft III Free Download